Boresighting is an alignment process by which the weapon tube centerline (centerline axis) and gunner's optical sighting system are referred to the same aiming point. This operation typically requires two people, a fire control system operator (or gunner) inside the vehicle and an assistant looking through the optical boresight telescope attached to an adapter/mandrel which is inserted into the bore of the weapon's barrel.
FIG. 1 depicts a tank 100 having a boresight telescope 160 including an eyepiece 161, an objective assembly 163, and a shank 164, mounted via an adapter (or mandrel) 150 which is inserted into the bore 18a of the gun barrel 18 for boresighting (or zeroing). On an armored vehicle such as the tank 100, the gun turret 20 is operated in azimuth and elevation to accomplish the boresight, and the gunner within the vehicle cannot see where the boresight telescope 160 is pointed. As a result, an individual looking through the eyepiece 161 of the boresight telescope 160 in front of the gun barrel 18 can be injured by unexpected movements of the gun barrel 18.
Some have disclosed direct view boresight cameras, but have generally been unable to demonstrate the accuracy claimed on their data sheets, with an actual tuning accuracy limited to no better than about +/−0.1 angular mils. These known boresight cameras are direct view, meaning the images obtained are parallel to the centerline axis of the bore of the weapon.